Losses in water supply assessed

Losses of up to 45% from the Clutha district's 24 water supply systems are "par for the course", a consultant says.

The Clutha District Council was presented with a water balance report prepared by Thomas Consultants Auckland engineer Richard Taylor, during its service delivery committee meeting in Balclutha yesterday afternoon.

The report detailed district-wide water system losses ranging from 11% (Moa Flat) to 45% (Milton).

Clutha's urban systems averaged 30.5%, and its rural systems 21.2% losses.

Despite the figures seeming "dramatic" to lay eyes, Mr Taylor, who has prepared similar reports for more than 15 councils nationwide, said they were not unusual.

"Clutha's overall system is typical of what you'd see anywhere in New Zealand.

"Some systems I've seen have losses in the 50% to 60%-plus range, so a top figure here of 45% is pretty good."

Due to the ageing nature of New Zealand's water supply networks, leaks were inevitable, Mr Taylor said.

"Water mains leaks don't fix themselves, and unless you're monitoring the system closely, large, unreported leaks are not uncommon.

"Combined with smaller, on-property losses, they accumulate over time to the sorts of figures we typically see in New Zealand.

"Overall, Clutha is doing a pretty good job."

From a customer service perspective, councils could cope with high losses due to the generally damp New Zealand climate, Mr Taylor said.

"Although a specific, localised leak might cause a noticeable pressure drop for a street or suburb, customers won't really notice any difference within the range of losses we're seeing in Clutha.

"It's more a question of economics for the council in question, and an appreciation of any environmental issues arising through those losses."

Council group manager service delivery Jules Witt said this was the first full audit of the district's water systems, and would provide a baseline for future comparison.

The report would also allow the council to better target areas requiring attention.

"Milton is very high, with relatively high losses in Balclutha [26%], Clydevale-Pomahaka [32%], and North Bruce [29%]. The process now is to recommend where best to spend funds to reduce costs to ratepayers."

Options to reduce losses included dropping water pressure, spot repair and gradual pipe renewal, Mr Witt said.

Zone metering would be put in place for Milton and Balclutha next year, allowing identification of high loss areas in the towns.

Targeted pipe replacements were likely to follow, he said.

"It's about getting the best bang for the ratepayer buck," he said.

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